The present invention relates to a comparator circuit used for an analog circuit technique and a digital/analog conversion technique.
Conventionally, in a circuit technique such as a differential chopper comparator or the like, an amplifier for feedback is generally used to stabilize an operating point at a certain reference voltage VREF.
FIG. 4 is a circuit configuration of a conventional comparator circuit having a feedback amplifier. Resistor elements R1 and R2 are used to prepare an intermediate voltage Vm between two outputs from a differential amplifier (or comparator) AMP1 as a level detector. A difference between the voltage Vm and the reference voltage VREF is amplified by the feedback amplifier and fed back to the AMP1, thereby to stabilize the operating point of the AMP1.
The structure as described above uses those resistor elements R1 and R2 that occupy a considerably large occupation area among circuit elements. However, if the occupation area is reduced to downsize the resistor elements, the resistance value is reduced and involves a problem that the gain of the outputs from the comparator (or outputs from the AMP1). In order to prevent decreases of the gain of the comparator outputs, the resistance values must be large and the occupation area of the resistors must accordingly be large.
Thus, in a conventional comparator circuit which uses a feedback amplifier for stabilizing an operating point, a feedback amplifier structure uses resistor elements which cause a problem that the occupation area of the resistor elements on a semiconductor chip is enlarged.